Hello,Does anyone have idea how to recalculate a path on the fly in pathfinding behaviour?Eg. unit1 has found path and its moving along but in the meanwhile an obstacle was created that makes it collide... at this point i need to recalculate the route... but how?

You have to do the path finding again for each unit as you normally do. You can use the regenerate collision map region or what it is called to regenerate the area of the newly added object, to reduce path finding time.